The SA Journal Diabetes & Vascular Disease Volume 18 No 2 (November 2021)

RESEARCH ARTICLE SA JOURNAL OF DIABETES & VASCULAR DISEASE 18 VOLUME 18 NUMBER 2 • November 2021 Resistivity index in the diagnosis and assessment of loss of renal function in diabetic nephropathy Yusuf Olanrewaju Jinadu, Yemi Raheem Raji, Samuel Oluwole Ajayi, Babatunde Lawal Salako, Ayodeji Arije, Solomon Kadiri Correspondence to: Yemi Raheem Raji Department of Medicine, University College Hospital, Ibadan, Oyo State, Nigeria e-mail: yemyrajj@yahoo.com Yusuf Olanrewaju Jinadu, Samuel Oluwole Ajayi, Ayodeji Arije, Solomon Kadiri Department of Medicine, University College Hospital, Ibadan, Oyo State, Nigeria Babatunde Lawal Salako Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria Previously published online in Cardiovasc J Afr 23 July 2021 S Afr J Diabetes Vasc Dis 2021; 18 : 18–24 Abstract Objective: The aim of this study was to determine the haemodynamics of the intrarenal arteries from the relationship between resistivity index (RI) and kidney function, and to identify the predictors of high RI among patients with diabetic nephropathy (DN) and those with diabetes mellitus (DM) without DN. Methods: Thiswasacross-sectional surveyof 133participants, comprising 40 subjects with DM without DN, 53 with DM with DN and 40 healthy controls. Information obtained was demographics, lifestyle, medical and medication histories, while anthropometric and blood pressure measurements were taken. Albuminuria and estimated glomerular filtration rate were determined and RI was measured using a Doppler ultrasound scan. Results: The mean intrarenal artery RIs were higher among the patients with DMwithout DN (0.60 ± 0.04) and the group with DM with DN (0.61 ± 0.04) than in the controls (0.56 ± 0.04) ( p = 0.02). Glycated haemoglobin (HbA 1c ) predicted high RI in the DM without DN group (OR 2.81; CI: 1.73–9.03) while hypertension (OR 3.60; CI: 1.06–12.22) predicted high RI in the DM with DN group. Conclusion: Elevated intrarenal artery RI was prevalent among patients with DM without DN and those with DM with DN, while elevated HbA 1c level and hypertension predicted elevated RI in subjects with DM without DN and those with DM with DN. Keywords: chronic kidney disease, diabetes mellitus, diabetic nephropathy, intrarenal artery haemodynamics, resistivity index The incidence of diabetes mellitus (DM), especially type 2, is rapidly growing worldwide. 1,2 Approximately 7.1 million Africans were said to be suffering from diabetes at the end of 2000 and it is projected to rise to 18.6 million by 2030. 3-5 Diabetic nephropathy (DN) is a major microvascular complication of DM and it is regarded as the leading cause of end-stage kidney disease (ESKD) worldwide. 6 DN not only contributes to increased morbidity and mortality among patients with ESKD but is also responsible for the huge cost of care needed for kidneyreplacement therapy. 7,8 In Nigeria, DN is the third leading cause of chronic kidney disease (CKD) and ESKD after hypertension and chronic glomerulonephritis. 9,10 Early detection of kidney disease among individuals with DM is carried out using the determination of urinary microalbuminuria and estimated glomerular filtration rate (eGFR). 11 These markers of kidney damage often lag behind the structural damages that may be ongoing in the kidneys. 12-14 Similarly, kidney ultrasonography is helpful in evaluating kidney disease chronicity, but often the findings on sonography are normal despite severe kidney dysfunction. 15 Furthermore, it has also been suggested that the routine measures of kidney function probably do not identify early structural and functional changes in individuals with DM. 16 Changes in the kidneys include haemodynamic disturbances within the glomerulus with increased blood flow and pressure and this occurs early in the course of DM, which over time contributes significantly to the development of glomerulosclerosis and its attendant proteinuria. 17 Micropuncture studies have shown in experimental studies of DM that there is an elevation of intraglomerular pressure even in the absence of systemic hypertension. 18 Therefore, investigations that assess blood flow haemodynamics may theoretically be useful in assessing early kidney dysfunction in individuals with DM. The use of Doppler ultrasonography to assess the haemodynamics of the glomeruli by measuring resistivity index (RI) has increased the prospect of early detection of DN. 19,20 RI has the advantage of being able to detect earlier changes and vascular damage preceding hyperfiltration and microalbuminuria. 20 The prospect of a tool that will detect kidney disease early among patients with DM offers a cost–benefit advantage to populations in low-resource setting, such as Nigeria and other low- and middle-income countries (LMICs). 21 Moreover, the accessibility and affordability of kidney-replacement therapy pose challenges to most patients in LMICs with ESKD. 22 The RI also has an advantage of being a non-invasive measurement. The objective of this study was to determine the relationship between RI and kidney function and identify the predictors of high RI among DM patients with DN and those with DM without DN. Methods This was a single-centre, cross-sectional study of 133 subjects that was carried out in the nephrology and endocrinology units of the Department of Medicine, University College Hospital, Ibadan, Nigeria. There were 53 subjects with DM with DN, 40 with DM without DN and 40 control subjects. The study was conducted over